The invention is directed to an immersion casting pipe.
In the continuous casting of flat products of steel, a casting pipe is used to direct the melt from a feed vessel into a mold. The mold has wide side walls and narrow side walls which maintain a distance of 50 to 100 mm between the wide side walls and define the narrow sides of the slab. The immersion casting pipe has been adapted to the mold format in such a way that the immersion casting pipe first forms a pipe piece which adjoins the casting vessel, then widens in cross section in the direction of the narrow side walls of the mold and narrows in a direction vertical thereto. Conventional immersion outlets have outlet openings which face in the direction of the narrow sides (see DE 37 09 188 A1) or which face more in the casting direction as is known, for example, from EP 0 403 808 A1. Finally, immersion outlets which only have an outlet opening in the casting direction are also known (see Steel and Iron (1991), No. 9, page 107). These immersion outlets enable satisfactory operation at a slab withdrawal speed of up to 3 m/min.
It may be observed in practical operation that the melt emerging from the immersion pipe has an unstable flow such that the melt entering the mold rocks back and forth between the right-hand and left-hand defining walls of the immersion outlet. This leads to turbulence at the surface of the casting melt which takes the form of a pulsating up-and-down movement inside the mold. At higher slab withdrawal speeds and consequently higher output through the immersion outlet, whirling occurs on the surface of the casting melt and particles of pulverized cast and slag are entrained in the melt and later occur as nonmetallic inclusions in the cast product. This whirling on the surface of the casting melt is caused at higher outputs by the higher kinetic energy in the stream of molten metal which leads to localized high turbulence in the melt sump or liquid phase. The outlet momentum of the molten stream cannot be uniformly reduced and eliminated in the forms of immersion pipes known from the prior art.